A liquid crystal display (LCD) is a type of flat panel display (FPD) which displays images by the property of the liquid crystal material. In comparison with other display devices, the LCD has the advantages in lightweight, compactness, low driving voltage and low power consumption, and thus has already become the mainstream product in the whole consumer market. In a traditional process of LCD panel, it comprises a front-end array process, a mid-end cell process and a back-end modulation process. The front-end array process is used to produce thin-film transistor (TFT) substrates (also called array substrates) and color filter (CF) substrates; the mid-end cell process is used to combine the TFT substrate with the CF substrate, then fill liquid crystal into a space therebetween, and cut to form panels with a suitable product size; and the back-end modulation process is used to execute an installation process of the combined panel, a backlight module, a panel driver circuit, an outer frame, etc.
An assembly of driver chips of the back-end modulation process is an assembling technology to combine the driver chips with the LCD panel. There are various packaging types of the driver chip for LCD, such as quad flat package (QFP), chip on glass (COG), tape automated bonding (TAB), chip on film (COF), etc, wherein the COF structure has flexibility and smaller circuit pitches, so as to become the main technology of the package of driver chips.
Referring now to FIG. 1, a top view of a traditional COF structure is illustrated in FIG. 1. Specially explaining, for conveniently describing, FIG. 1 is shown in simplification, wherein the number of the traces is simplified, and some of details which are unrelated to the explanation are also omitted. As shown in FIG. 1, a COF structure of a liquid crystal panel comprises a flexible substrate 90, an output edge 91, a wire bonding portion 92, and a fan-out trace portion 93. The output edge 91 is disposed on an edge of the flexible substrate 90, and used to be connected with a liquid crystal panel (not shown). The wire bonding portion 92 having a plurality of lead strips (unlabeled) of elongated shape is disposed on the flexible substrate 90, and is located at a center of the flexible substrate 90. A long direction of the lead strips of the wire bonding portion 92 is perpendicular to the output edge 91. The fan-out trace portion 93 has a plurality of traces which are with a fan shape and respectively connect one end of the lead strips of the wire bonding portion 92 to the output edge 91. Besides, the wire bonding portion 92 are electrically connected with a driver chip (not shown).
As shown in FIG. 1, two sides of the wire bonding portion 92 are provided with wire bonding alignment marks 94. Because locations near two sides of the fan-out trace portion 93 are necessary to reserve a greater height D for layout, on one hand, it will occupy an available space of the fan-out trace portion 93, and on the other hand, it makes the height of the fan-out trace portion 93 increased, so that it is disadvantageous in a design trend of narrow frame edge of a liquid crystal panel.
As a result, it is necessary to provide a COF structure for a liquid crystal panel to solve the problems existing in the conventional technologies.